White and yellow traffic markings used for demarcating traffic lanes is a common sight on almost all roads. These markings ensure safe driving conditions under varying weather conditions. The term "roads" generally means routes, highways, airport runways, exit and entry ramps, passes, pavements, side walks or parking lots for vehicles, such as, autos, bikes, trucks, and the roads are usually paved with asphalt, wood, metal or from concrete, generally made from Portland cement. The majority of these traffic markings, such as, solid, transverse or interrupted stripes, are paint-based and traditionally include solvent-borne binders, which are predominantly alkyds and chlorinated rubber-modified alkyds. However, since the 1980s environmentally safer waterborne traffic paints have also been used. These waterborne traffic paints are primarily based on acrylic emulsions and produce dramatically lower VOC emissions than traditional solvent-based traffic paints.
However, these conventional waterborne traffic markings tend to be less wear resistant than traditional alkyd based traffic paints when exposed to traffic conditions, such as, wear and tear resulting from exposure to vehicular traffic. The term wear resistance means the degree of resistance of the traffic markings to detaching from the road surface when the marking is exposed to the traffic conditions and to UV degradation. The wear resistance is expressed as the percentage area of a film of traffic marking still remaining on the road surface after its extended exposure to such traffic conditions. It has been found that substantial portions of conventional waterborne traffic markings tend to wear away in less than a few months after exposure to such accelerated traffic conditions.
Attempts have been made to solve the problem of the excessive traffic marking wear. For example, Clinnin et al. in the U.S. Pat. No. 5,340,870 describe a fast dry wear resistant traffic marking paint containing a hydrophobic polymer emulsion polymerized in the presence of a water-soluble support polymer that is polymerized from a monomer mixture consisting of acid, styrene and substituted styrene monomers, preferably in equal proportions. One of the problems associated with such a styrene based traffic paint is that it tends to degrade over time when exposed UV radiation from sun that is typically experienced by traffic markings. Thus, a need still exists for a waterborne traffic paint having improved wear resistance under typical traffic conditions.